Exterior brickwork cracks and pointing deterioration in 60's extension

We have a 10' x 7' single storey dining extension on our 1930s corner terrace. The extension was added in the 1960s, and uses clay bricks and roof tiles. There is a stepped crack above the side window of the extension, going up about two feet - mostly following the mortar but going through the middle of two bricks also - which are now starting to crumble. There is a further small crack around 6 inches long underneath the window on the longer wall of the extension that goes right through - we filled with Ronseal. Recently, we have had damp in the corner, and have noticed a clay tile sticking up slightly at eaves level - it doesn't push down again so I've let it alone, and we have discovered an earlier botch job under the eaves in the corner, where there is a hole around 2 inches diameter that looks to have been badly plugged with a lump of cement. Are these combined problems something that one tradesman would be able to fix decently for not too much money (none of it would need scaffold) or are we likely to be living with a more serious problem? Would it be necessary to repoint all the brickwork rather than just the damaged areas? I am presuming it would need a traditional lime-based mortar (and that the existing mortar is cement based hence the cracking) as we are on solid clay ground (Oxford).